Motor driver, motor driven by the motor driver, and apparatus employing the motor

ABSTRACT

A motor driver includes a first signal selector and a second signal selector. The first signal selector is used for selecting a signal to be supplied to an energizing unit of driving coils, and selects either one of a normal energizing pattern signal supplied from an energizing signal generator or a signal from the second signal selector based on a signal from an over-current detector. The second signal selector selects either one of a first non-normal energizing pattern signal from a first energizing signal output unit or a second non-normal energizing pattern signal from a second energizing signal output unit based on a signal from a rotary direction detector.

This application is a U.S. national phase application of PCTInternational Application PCT/JP2004/006062 dated Apr. 27, 2004.

TECHNICAL FIELD

The present invention relates to a motor driver, motors to be driven bythe motor driver, and apparatuses such as air conditioners, aircleaners, and water heaters, which are equipped with the motor.

BACKGROUND ART

A variety of motors employed in, e.g. air conditioners, often use apermanent-magnet brush-less DC motor (hereinafter referred to simply asa motor), of which rotor is equipped with permanent magnets, takingadvantage of its long service-life, high reliability, and easy speedcontrol.

A conventional motor driver for driving such a motor as discussed aboveis disclosed in Japanese Patent Application Non-Examined Publication No.2002-369576. This motor driver has a structure such that if the rotor isdriven in a reverse direction by external force or inertia when thedriver is about to start driving the motor, the driver is prohibitedfrom driving the motor. This structure prevents a high current fromrunning through the motor driving coil wound on the stator teeth, sothat no demagnetiziation occurs in the rotor magnets.

To be more specific, a control unit disposed in the motor driver detectsa rotary direction of the rotor based on changes of a position detectingsignal supplied from a Hall sensor prepared in the motor. When thedriver is about to start driving the motor, the control unit permitsdriving the motor and outputs a control signal for turning ontransistors in the inverter section provided that the rotor is halted orthe rotor rotates in the same direction as the direction the motor isabout to rotate along. The output of the control signal entails adriving current to run through the motor driving coils, so that themotor starts rotating.

On the other hand, when the driver is about to start driving the motor,the control unit prohibits the motor from rotating and outputs a controlsignal for turning off every transistor in the inverter section providedthat the rotor rotates in the reverse direction to the direction themotor is about to rotate along. The output of the control signal resultsin supplying no driving current to the motor driving coils. Thisstructure prevents a high current from running through the motor drivingcoils, so that no demagnetiziation occurs in the rotor magnets.

FIG. 6 shows a circuit diagram of another conventional motor driver, andFIG. 7 shows signal waveforms, of which parts illustrate signals innormal energizing and the remaining part illustrates the signals innon-normal energizing of the motor driver shown in FIG. 6.

As shown in FIG. 6, in the motor driver normally energized, energizingsignal generator 190 outputs energizing signals UH0, UL0, VH0, VL0, WH0,and WL0. Those signals control six transistors, 131, 132, 133, 134, 135and 136 to be turned on or off sequentially. Those six transistors formenergizing unit 120. This control entails the current supply to thethree-phase driving coils 111, 113 and 115 to be switched sequentiallyas signals U, V and W shown in FIG. 7, thereby rotating the motor. Thedriving coils are equipped to the stator of the motor.

The foregoing motor driver stops the current supply to driving coils111, 113 and 115 when the current supplied to energizing unit 120increases up to a given value. This action is referred to as non-normalenergizing. To be more specific, when the current increases, overcurrent detector 170 outputs signal OC, which is received by signalselector 150. Selector 150 then switches signals supplied fromenergizing signal generator 190 into signals UH1, UL1, VH1, VL1, WH1,and WL1 supplied from energizing signal output unit 140 beforeoutputting them to energizing unit 120. Those signals supplied fromoutput unit 140 turn off all the transistors 131–136 in energizing unit120. This mechanism stops the current supply to driving coils 111, 113and 115.

There are methods other than the foregoing method for stopping thecurrent supply to the driving coils, e.g. supply of a signal to turn ontransistors 131, 133, 135 and turn off transistors 132, 134, 136, or theother way around, i.e. to turn on transistors 132, 134, 136 and turn offtransistors 131, 133, 135.

However, assume that the latter instance is taken as an example ofconventional motor drivers, when all transistors 131–136 in energizingunit 120 are turned off, the energy stored in three-phase driving coils111, 113 and 115 travels through any one of flywheel diodes 121–126,i.e. runs as a current. This run of current sharply changes voltages U,V and W across the driving coils as shown in FIG. 7. As a result, thedriving coils vibrate, which sounds audible and sometimes causes noises.Normal energizing and non-normal energizing repeat at a variety ofintervals, so that the repeat causes grating noises if it falls withinthe audio frequency.

As discussed previously, the another method for stopping the currentsupply to the driving coils 111, 113 and 115 is available: shorting thedriving coils each other by turning on transistors 131, 133, 135 andturning off transistors 132, 134, 136, or the other way around, i.e.turning off transistors 131, 133, 135 and turning on transistors 132,134, 136. The current supply from power supply Vdc can be halted throughthose methods; however, back electromotive force (BEMF) is generated inthe driving coils during the spin and a current caused by the BEMF willflow.

The methods discussed above have the effect of reducing the currentrunning through the driving coils in the case of positive spin(spin-direction driven by the normal energizing). However, in anapparatus of which fan is driven by a motor, when the fan is rotated ina reverse direction (direction opposite to the normal energizingdirection) by some external force such as wind energy, the currentrunning through the driving coils sometimes further increases. Theincrease of current violates the over-current regulating function thatshould be activated in the normal energizing state. This violationleaves a problem in actual operation.

DISCLOSURE OF THE INVENTION

The motor driver of the present invention comprises the followingelements:

(a) an energizing unit for supplying a current to the driving coils ofthe motor;

(b) an energizing signal generator for generating a normal generatingpattern which the energizing unit performs to the driving coils;

(c) a first energizing signal output unit in which a first non-normalenergizing pattern is stored;

(d) a second energizing signal output unit in which a second non-normalenergizing pattern different from the first pattern is stored;

(e) a rotary direction detector for detecting a rotary direction of themotor;

(f) an over current detector for detecting a current of the motor;

(g) a first signal selector for selecting a signal to be supplied to theenergizing unit; and

(h) a second signal selector for selecting a signal to be supplied tothe first signal selector.

The first signal selector receives a signal from the energizing signalgenerator, a signal from the second signal selector, and a signal fromthe over-current detector, then selects either one of the signal fromthe energizing signal generator or the signal from the second signalselector based on the signal from the over-current detector beforeoutputting the signal selected.

The second signal selector receives a signal from the first energizingsignal output unit, a signal from the second energizing signal outputunit, and a signal from the rotary direction detector, then selectseither one of the signal from the first energizing signal output unit orthe signal from the second energizing signal output unit based on thesignal from the rotary direction detector before outputting the signalselected.

The foregoing structure allows decreasing noises while the currentregulating function is kept alive against an over current running in themotor.

The present invention also refers to motors driven by the foregoingmotor driver, and apparatuses, which include driven sections such as afan, driven by the motors.

The motors and the apparatuses of the present invention can achievelowering noises while the current regulating function is kept aliveagainst an over current running in the motor.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 shows a circuit diagram of a motor driver in accordance with anexemplary embodiment of the present invention.

FIG. 2 illustrates an operation of the motor driver shown in FIG. 1.

FIG. 3A shows a structure of an indoor unit of an air-conditioner inaccordance with an exemplary embodiment of the present invention.

FIG. 3B shows a structure of an outdoor unit of an air-conditioner inaccordance with an exemplary embodiment of the present invention.

FIG. 4 shows a structure of a water heater in accordance with anexemplary embodiment of the present invention.

FIG. 5 shows a structure of an air cleaner in accordance with anexemplary embodiment of the present invention.

FIG. 6 shows a circuit diagram of a conventional motor driver.

FIG. 7 illustrates an operation of the conventional motor driver shownin FIG. 6.

BEST MODE FOR PRACTICING THE INVENTION

The exemplary embodiment of the present invention is demonstratedhereinafter with reference to the accompanying drawing. FIG. 1 shows acircuit diagram of a motor driver in accordance with an exemplaryembodiment of the present invention, and FIG. 2 illustrates an operationof the motor driver shown in FIG. 1.

The motor driver shown in FIG. 1 in accordance with the exemplaryembodiment of the present invention comprises the following elements:

(a) energizing unit 20 for supplying a current to the driving coils ofthe motor;

(b) energizing signal generator 90 for generating a normal generatingpattern which the energizing unit performs to the driving coils;

(c) first energizing signal output unit 41 in which a first non-normalenergizing pattern is stored;

(d) second energizing signal output unit 42 in which a second non-normalenergizing pattern different from the first pattern is stored;

(e) rotary direction detector 60 for detecting a rotary direction of themotor;

(f) over current detector 70 for detecting a current of the motor;

(g) first signal selector 51 for selecting a signal to be supplied toenergizing unit 20; and

(h) second signal selector 52 for selecting a signal to be supplied tofirst signal selector 51.

First signal selector 51 receives a signal from energizing signalgenerator 90, a signal from second signal selector 52, and a signal fromover-current detector 70, then selects either one of the signal fromenergizing signal generator 90 or the signal from second signal selector52 based on the signal from over-current detector 70 before outputtingthe signal selected to energizing unit 20.

Second signal selector 52 receives a signal from first energizing signaloutput unit 41, a signal from second energizing signal output unit 42,and a signal from rotary direction detector 60, then selects either oneof the signal from first energizing signal output unit 41 or the signalfrom second energizing signal output unit 42 based on the signal fromrotary direction detector 60 before outputting the signal selected tofirst signal selector 51.

In this exemplary embodiment depicted in FIG. 1, a three-phase motor, inwhich phase-U driving coil 11, phase-V driving coil 13, and phase-Wdriving coil 15 are coupled like a star, is driven by rectangularenergizing waveform having 120 degrees in electrical angles. In thedescriptions of this embodiment, the normal energizing refers to theenergizing based on an output signal from energizing signal generator90, and in the normal energizing state, the motor is driven for itsoriginal purpose, namely, phase-U, phase-V and phase-W are sequentiallydriven by rectangular waveforms having 120 degrees in electrical angles.

The non-normal energizing in this embodiment refers to the energizingbased on either one of an output signal from first energizing outputunit 41, in which a specific energizing pattern (first non-normalenergizing pattern) is stored, or second energizing output unit 42, inwhich an energizing pattern different from the foregoing specificenergizing pattern is stored. In other words, the three-phase drivingcoils are energized differently from the normal energizing status. Forinstance, the three-phase driving coils become open, i.e. electricallyisolated from energizing unit 20, and as a result, the motor is left infree-run status. Another instance is that the three-phase driving coilsare shorted with each other, and as a result, the motor is left inbraking status.

In energizing unit 20, three energizing elements, e.g. field effecttransistors (FET) 31, 33 and 35 form an upper arm, and in a similarmanner, another three FET transistors 32, 34, and 36 form a lower arm,so that those six energizing elements form an inverter section.

A first terminal of phase-U driving coil 11 is coupled to a connectingpoint between transistors 31 and 32. A first terminal of phase-V drivingcoil 13 is coupled to a connecting point between transistors 33 and 34,and a first terminal of phase-W driving coil 15 is coupled to aconnecting point between transistors 35 and 36. Respective secondterminals of phase-U coil 11, phase-V coil 13 and phase-W coil 15 arecoupled with each other, thereby forming neutral point N.

Between every source and drain of respective transistors 31, 32, 33, 34,35 and 36, flywheel diodes 21, 22, 23, 24, 25 and 26 are connectedrespectively. A dc power supply (not shown) applies output voltage Vdcto energizing unit 20, and powers the foregoing three-phase drivingcoils via energizing unit 20.

Six output signals UH, UL, VH, VL, WH and WL from first signal selector51 are applied to the respective gates of transistors 31–36 via gatedriver 27. Energizing unit 20 is thus formed of gate-driver 27, the sixtransistors and the six diodes.

Energizing signal generator 90 outputs signals UH0, UL0, VH0, VL0, WH0,and WL0. Those signals stay at level H while the electric angle is keptat 120 degrees, and stay at level L while it is kept at 240 degrees asshown in FIG. 2. During the normal energizing, when signal UH0 stays atlevel H or level L, signal UH also falls at level H or level L even viafirst signal selector 51. When signal UL0 stays at level H or level L,signal UL falls at level H or level L even via signal selector 51. Whensignal VH0 stays at level H or level L, signal VH also falls at level Hor level L via signal selector 51. When signal VL0 stays at level H orlevel L, signal VL also falls at level H or level L via signal selector51. When signal WH0 stays at level H or level L, signal WH also falls atlevel H or level L via signal selector 51. When signal WL0 stays atlevel H or level L, signal WL also falls at level H or level L even viasignal selector 51.

Signals UH, UL, VH, VL, WH and WL are applied to the gates oftransistors 31, 32, 33, 34, 35 and 36 respectively via gate-driver 27.Those transistors are turned on when corresponding signals UH, UL, VH,VL, WH and WL stay at level H, and turned off when those signals stay atlevel L.

On the other hand, first energizing signal output unit 41 outputssignals UH1 a, UL1 a, VH1 a, VL1 a, WH1 a and WL1 a. Output unit 41stores an energizing pattern (a first non-normal energizing pattern)which outputs all of those signals at level L. Those signals becomesignals UH, UL, VH, VL, WH and WL, all staying at level L, via secondsignal selector 52 and first signal selector 51.

Signals UH, UL, VH, VL, WH and WL are applied to the gates oftransistors 31, 32, 33, 34, 35 and 36 respectively via gate array 27,thereby turning off all transistors 31, 32, 33, 34, 35 and 36. As aresult, three-phase driving coils 11, 13 and 15 are isolated from bothof the positive side and negative side of the dc power supply, so thatall the driving coils become open and fall in non-normal energizingstatus. At this time, the motor falls in free-run status.

Next, second energizing signal output unit 42 outputs signals UH1 b, UL1b, VH1 b, VL1 b, WH1 b and WL1 b. Output unit 42 stores an energizingpattern (a second non-normal energizing pattern) which outputs signalsUH1 b, VH1 b and WH1 b at level L and signals UL1 b, VL1 b and WL1 b atlevel H. Those signals become signals UH, VH, WH at level L, and UL, VL,WL at level H via second signal selector 52 and first signal selector51.

Signals UH, UL, VH, VL, WH and WL are applied to the gates oftransistors 31, 32, 33, 34, 35 and 36 respectively via gate-driver 27,so that transistors 31, 33, 35 forming the upper arm of energizing unit20 are turned off, and transistor 32, 34, 36 forming the lower arm areturned on. Then the respective first terminals of three-phase drivingcoils 11, 13, 15 are electrically isolated from the positive side of thedc power supply and coupled to the negative side (grounding) of the dcpower supply. As a result, driving coils 11, 13, 15 are shorted witheach other. At this time, the motor falls in braking status, which isshown as non-normal energizing status in FIG. 2.

Meanwhile, second energizing signal output unit 42 can store the secondnon-normal energizing pattern, which outputs signals UH1 b, VH1 b, WH1 bat level H, and signals UL1 b, VL1 b, WL1 b at level L. In this case,transistors 31, 33, 35 forming the upper arm of energizing unit 20 areturned on, and transistors 32, 34, 36 forming the lower arm are turnedoff. Then the respective first terminals of driving coils 11, 13, 15 areelectrically isolated from the negative side (grounding) of the dc powersupply, and connected to the positive side of the dc power supply. As aresult, driving coils 11, 13 and 15 are shorted with each other, and themotor falls in braking status.

Rotary direction detector 60 detects a rotary direction of the motorbased on a change of a rotor-position detecting signal supplied from aposition sensor disposed in the motor, then outputs given signal DM.Over-current detector 70 detects a current flowing in energizing unit20, and when detecting a current over a given value, detector 70 outputsgiven signal OC.

Second signal selector 52 selects either one of a signal from firstenergizing signal output unit 41 or a signal from second energizingsignal output unit 42 based on signal DM supplied from rotary directiondetector 60, then outputs the signal selected to first signal selector51.

First signal selector 51 selects either one of a signal from energizingsignal generator 90 or a signal from second signal selector 52 based onsignal OC supplied from over-current detector 70, then outputs signalsUH, UL, VH, VL, WH, WL to energizing unit 20. Those signals aretransformed, at gate driver 27, into voltages adequate for activatingtransistors 31, 32, 33, 34, 35 and 36, then supplied to the gates of thecorresponding transistors.

An operation of the motor driver discussed above is demonstratedhereinafter with reference to FIG. 2, which shows changes of signals atthe transition from the normal energizing to the non-normal energizing.

During the normal energizing period, the driving coils of the motor aredriven by a rectangular energizing waveform having 120 degrees inelectrical angles; however, when over-current detector 70 detects anover-current, the normal energizing is changed to the non-normalenergizing. This change is carried out by the following operation offirst signal selector 51 based on signal OC supplied from over-currentdetector 70: During the non-normal energizing period, based on signal OCfrom over-current detector 70, first signal selector 51 switches outputsignals UH, UL, VH, VL, WH, WL into signals UH1, UL1, VH1, VL1, WH1, WL1supplied from second signal selector 52, from signal UH0, UL0, VH0, VL0,WH0, WL0 supplied from energizing signal generator 90 during the normalenergizing period.

Further, based on signal DM supplied then from rotary direction detector60, second signal selector 52 selects as output signals UH1, UL1, VH1,VL1, WH1, WL1 either one of UH1 a, UL1 a, VH1 a, VL1 a, WH1 a, WL1 a(first non-normal energizing pattern) supplied from first energizingsignal output unit 41 or UH1 b, UL1 b, VH1 b, VL1 b, WH1 b, WL1 b(second non-normal energizing pattern) supplied from second energizingsignal output unit 42.

The motor driven by the motor driver of the present invention ismounted, e.g. in an outdoor unit of an air-conditioner, and assume thatits driving object (driven unit) is a fan. Then it is possible that thefan is rotated in a reverse direction (opposite to a driving directionby the normal energizing waveform) by a strong blow such as typhoon, andthe motor thus rotates in the reverse direction.

In this state, when over-current detector 70 detects an over current,turning off all transistors 31–36 of energizing unit 20 can reduce thecurrent running through driving coils 11, 13, 15. Therefore, secondsignal selector 52 selects a signal (the first non-normal energizingpattern) from first energizing signal output unit 41, and first signalselector 51 selects a signal (in this case, the first non-normalenergizing pattern) from second signal selector 52, thereby turning offall transistors 31–36 of energizing unit 20. The function of currentregulation to the driving coils is thus alive. This operation is similarto that of the prior art, and accompanied by audible noises; however, itis rare that the motor rotates in a reverse direction caused by a strongblow, and yet, the strong blow produces other noises which can cancelthe audible noises.

Next, during the positive rotation (rotated by the normal energizingwaveform) of the motor, when the motor current increases and an overcurrent is detected, second signal selector 52 selects a signal fromsecond energizing signal output unit 42 (the second non-normalenergizing pattern). Further, first signal selector 51 selects a signalsupplied from second signal selector 52 (in this case, the secondnon-normal energizing pattern). Those selections turns off transistors31, 33, 35 forming the upper arm of energizing unit 20, and turns ontransistors 32, 34, 36 forming the lower arm. As a result, driving coils11, 13, 15 are isolated from the positive side of the dc power supply,and those coils are shorted with each other. As such, in the case ofpositive rotation, it is not necessarily to turn off all the transistorsfor reducing the coil current, and the current regulation stilleffectively works. This operation does not involve drastic changes involtages U, V, W applied to the driving coils as shown in FIG. 2, sothat the noises can be suppressed.

As discussed above, the present invention can reduce noises while thecurrent regulating function is kept alive at an over-current in themotor.

A variety of signal-processing in this embodiment can be done byhardware, such as analog or digital circuitry. They can be done also bysoftware using a microcomputer, digital signal processor (DSP). Thesignal processing circuit can be integrated into an IC or an LSI.

The exemplary embodiment discussed above is not only effective when amotor is driven by a rectangular energizing waveform having 120 degreesin electrical angles, but also effective driven by other waveforms, e.g.150 degrees in electrical angles or sine energizing waveform. Thisembodiment is also effective when the pulse width modulation (PWM)driving or pulse amplitude modulation (PAM) driving is used.

Next, several examples of motors driven by the motor driver of thepresent invention and apparatuses employing non-driving parts, e.g. afan, driven by the motor are described hereinafter. In the followingdescriptions, the motor driver is independent of the motor; however, itcan incorporate the motor.

FIG. 3A shows a structure of an indoor unit of an air-conditioner inaccordance with this embodiment of the present invention, and FIG. 3Bshows a structure of an outdoor unit of the air-conditioner inaccordance with the embodiment.

In FIG. 3A, indoor unit 301 includes motor 301 therein, and cross-flowfan 312, which is a driven part, is attached to the shaft of motor 301driven by motor driver 314. Motor driver 314 powers motor 301 to spin,which is accompanied by spinning of cross-flow fan 312. The spin of fan312 blows the air conditioned by an indoor heat exchanger (not shown)into the room. Use of the motor driver demonstrated in the foregoingembodiment as motor driver 314 allows reducing noises of the indoor unitwhile the current regulating function is kept alive at an over currentin the motor.

In FIG. 3B, outdoor unit 320 includes motor 302 therein, and propellerfan 322, which is a driven part, is attached to the shaft of motor 302driven by motor driver 324. Motor driver 324 powers motor 302 to spin,which is accompanied by spinning of propeller fan 322. The spin of fan322 blows the air to an outdoor heat exchanger (not shown). Use of themotor driver demonstrated in the foregoing embodiment as motor driver324 allows reducing noises of the outdoor unit while the currentregulating function is kept alive at an over current in the motor.

FIG. 4 shows a structure of a water heater in accordance with thisembodiment of the present invention. In FIG. 4, water heater 330includes motor 303 therein, and fan 332, which is a driven part, isattached to the shaft of motor 303 driven by motor driver 334. Motordriver 334 powers motor 303 to spin, which is accompanied by spinning offan 332. The spin of fan 332 blows the air necessary for combustion to afuel vaporizing chamber (not shown). Use of the motor driverdemonstrated in the foregoing embodiment as motor driver 334 allowsreducing noises of the water heater while the current regulatingfunction is kept alive at an over current in the motor.

FIG. 5 shows a structure of an air cleaner in accordance with thisembodiment of the present invention. In FIG. 5, air cleaner 340 includesmotor 304 therein, and air circulating fan 342, which is a driven part,is attached to the shaft of motor 304 driven by motor driver 344. Motordriver 344 powers motor 304 to spin, which is accompanied by spinning offan 342. The spin of fan 342 circulates the air. Use of the motor driverdemonstrated in the foregoing embodiment as motor driver 344 allowsreducing noises of the water heater while the current regulatingfunction is kept alive at an over current in the motor.

As discussed above, use of the motor driven by the motor driver of thepresent invention in a variety of apparatuses allows reducing noises ofthe apparatuses while the current regulating function is kept alive atan over current in the motor.

INDUSTRIAL APPLICABILITY

The motor driver of the present invention comprises the followingelements: (a) an energizing unit for supplying a current to the drivingcoils of the motor; (b) an energizing signal generator for generating anormal generating pattern; (c) a first energizing signal output unit inwhich a first non-normal energizing pattern is stored; (d) a secondenergizing signal output unit in which a second non-normal energizingpattern different from the first pattern is stored; (e) a first signalselector for selecting a signal to be supplied to the energizing unit;(f) a second signal selector for selecting a signal to be supplied tothe first signal selector; (g) a rotary direction detector for detectinga motor rotating direction; and (h) an over current detector fordetecting an over current of the motor.

The first signal selector selects either one of the signal from theenergizing signal generator or the signal from the second signalselector based on the signal from the over-current detector beforeoutputting the signal selected. The second signal selector selectseither one of the signal from the first energizing signal output unit orthe signal from the second energizing signal output unit based on thesignal from the rotary direction detector before outputting the signalselected.

Use of the motor, which is driven by the motor driver of the presentinvention, in a variety of apparatuses allows reducing noises of theapparatuses while the current regulating function is kept alive at anover current in the motor.

1. A motor driver comprising: (a) an energizing unit for supplying acurrent to a driving coil of a motor; (b) an energizing signal generatorfor generating a normal generating pattern which the energizing unitperforms to the driving coil; (c) a first energizing signal output unitin which a first non-normal energizing pattern is stored; (d) a secondenergizing signal output unit in which a second non-normal energizingpattern different from the first pattern is stored; (e) a rotarydirection detector for detecting a rotary direction of the motor; (f) anover current detector for detecting a current of the motor; (g) a firstsignal selector for selecting a signal to be supplied to the energizingunit; and (h) a second signal selector for selecting a signal to besupplied to the first signal selector, wherein the first signal selectorreceives a signal from the energizing signal generator, a signal fromthe second signal selector, and a signal from the over-current detector,then selects either one of the signal from the energizing signalgenerator or the signal from the second signal selector based on thesignal from the over-current detector before outputting the signalselected, wherein the second signal selector receives a signal from thefirst energizing signal output unit, a signal from the second energizingsignal output unit, and a signal from the rotary direction detector,then selects either one of the signal from the first energizing signaloutput unit or the signal from the second energizing signal output unitbased on the signal from the rotary direction detector before outputtingthe signal selected.
 2. The motor driver of claim 1, wherein the firstnon-normal energizing pattern is used for controlling an energizingelement in the energizing unit so that the driving coil can be opened,and the second non-normal energizing pattern is used for controlling theenergizing element in the energizing unit so that the driving coil canbe shorted with each other.
 3. A motor driven by the motor driver asdefined in claim
 1. 4. A motor driven by the motor driver as defined inclaim
 2. 5. An apparatus including a driven part which is driven by themotor as defined in claim
 3. 6. An apparatus including a driven partwhich is driven by the motor as defined in claim
 4. 7. The apparatus asdefined in claim 5, wherein the driven part is a fan.
 8. The apparatusas defined in claim 6, wherein the driven part is a fan.